There are many problems associated with the production of oil and gas resources. For example, it is very common for oil production wells to reach the end of their life, while there is still a substantial amount of oil in place (OIP) within the formation. Engineers may then to decide whether to shut in the well or stimulate the well using enhanced oil recovery (EOR) methods ranging from water flooding to steam flooding to injection of carbon dioxide and injection of solvents.
Likewise, even during peak production of a well, a well may have to be shut in due to paraffin plugging the production tubing. This can cause several problems ranging from reduced production to parting or breaking of the sucker rod connected to the surface pump jack.
Another problem associated with most oil and gas wells is produced water. When the water reaches the surface it is separated from the oil or gas and then must be treated prior to final disposition.
Recently, primarily due to high crude oil prices many exploration companies are turning to unconventional heavy oil resources (API<22) such as oil sand bitumen, oil shale kerogen as well as heavy oil itself. Canada contains the largest known oil sand reserves estimated at over 1 trillion recoverable barrels of bitumen. Likewise, the largest known unconventional petroleum or hydrocarbon resource can be found in the Green River Formation in Colorado, Wyoming and Utah. Worldwide oil shale reserves are estimated around 2.9-3.3 trillion barrels of shale oil while the Green River Formation reserves alone are estimated to contain between 1.5-2.6 trillion barrels.
However, emerging issues with respect to the renewed interest in oil shale development range from water resources, to green house gas emissions to basic infrastructure needs. Likewise, the Canadian oil sands has its own problems ranging from very large tailings ponds to a lack of upgrading capacity for the bitumen recovered from the oil sands. In addition, the steam assisted gravity drainage (SAGD) process utilizes copious amounts of energy to produce steam. Two problems associated with producing steam are first the source of water and removing its contaminants that may be deposited upon boiler tube walls and second recovering the latent heat within the steam when injected downhole.
Likewise, there are many proponents suggesting CO2 injection as means for recovering heavy oil, oil sand and oil shale. As recently as Apr. 4, 2007 Schlumberger's scientific advisor on CO2, T. S. (Rama) Ramakrishnan has stated, “The research for efficient heavy oil recovery is still wide open. Steam flooding is the tried and trusted method, but we need to move forward. Having said that, I do not think advances will come about by refining current practices or expanding an existing research pilot—we need a step-change vis-à-vis enhancing heavy oil recovery. Oil at $60/bbl should be enough to provide the impetus.”
Shell Oil Company has been demonstrating its freeze-wall and in situ conversion process (ICP) for recovering kerogen from the Green River Formation located in Colorado's Piceance Basin. Although Shell has patented various aspects of the process, two of the impediments to large volume production of oil shale using ICP are the type of downhole heater and the formation's constituents. U.S. Pat. No. 7,086,468 and the family of other patents and published patent applications based on U.S. Provisional Patent Application No. 60/199,213 (Apr. 24, 2000), 60/199,214 (Apr. 24, 2000) and 60/199,215 (Apr. 24, 2000) provide detailed descriptions of the various prior art aboveground and in situ methods of retorting oil shale, all of which are hereby incorporated by reference in their entirety. Moreover, updated information regarding aboveground and in situ methods of retorting oil shale in the Green River Formation are described in “Converting Green River oil shale to liquid fuels with Alberta Taciuk Processor: energy inputs and greenhouse gas emissions” by Adam R Brandt (Jun. 1, 2007) and “Converting Green River oil shale to liquid fuels with the Shell in-situ conversion process: energy inputs and greenhouse gas emissions” by Adam R Brandt (Jun. 30, 2007), both of which are available at http://abrandt.berkeley.edu/shale/shale.html and are hereby incorporated by reference in their entirety.
What is unique about the Green River Formation oil shale is that it has a high content of Nahcolite. Nahcolite is commonly referred to as baking soda which is sodium bicarbonate (NaHCO3). Another active player in oil shale development, ExxonMobil, has developed an in situ conversion process for oil shale that is rich in Nahcolite. The process incorporates recovering kerogen while converting sodium bicarbonate or Nahcolite to sodium carbonate. ExxonMobil claims that the pyrolysis of the oil shale should enhance leaching and removal of sodium carbonate during solution mining.
Now, returning back to Shell's ICP for oil shale, the two largest problems to overcome are that baking soda can be used as a heating insulator and that oil shale is not very permeable. Thus using conventional heat transfer methods such as conduction and convection require a long period of time in addition to drilling many wells and incorporating many heaters close to one another.
Although in situ processes are rapidly developing for both oil shale and oil sands, surface processing is currently the leader for oil sands. Retorting of oil shale has been around since the early 1970's. Recently, retorting has been applied to oil sands. Once again the major problem with retorting either oil sand or oil shale is that the minerals and metals act to retard heat transfer. However, the single largest difference between oil shale and oil sand is that sodium carbonate is a known electrolyte. Likewise, oil sand contains electrolytes in the form of other salts.
While melting oil shale in a carbon crucible the inventor of the present invention has recently unexpectedly discovered a method for carbonizing oil shale with plasma electrolysis while simultaneously separating solids, liquids and gases. The process is based upon using the same mineral that is widespread in the Green River Formation—Baking Soda.